National Sleep Foundation

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Chapter 3: Sleep-Related Breathing Disorders

What is Obstructive Sleep Apnea Syndrome?

Obstructive Sleep Apnea Syndrome (OSAS) is the most common form of sleep apnea, and is characterized by upper airway obstructions that occur repeatedly during sleep and cause breathing to stop (“apnea”), when the obstruction is complete, or to be shallower than normal (“hypopnea”), when the obstruction is partial.

These obstructive events usually result in measurable drops in blood oxygen saturation, which returns to baseline levels when the person’s breathing resumes. Episodes of OSAS typically end with the person waking up briefly in order to reopen his or her airway.

People who have OSAS snore loudly between episodes and can also gasp and/or choke. As a result of the pattern of airway obstruction and multiple arousals that occur during the night, people with OSAS have sleep fragmentation and often experience excessive daytime sleepiness (EDS).